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    SubjectRe: Back to the future.
    On Thu, Apr 26, 2007 at 05:38:07PM -0400, Theodore Tso wrote:
    > On Fri, Apr 27, 2007 at 06:08:01AM +1000, Nigel Cunningham wrote:
    > > We tried that. It would need some work. IIRC remounting filesystems
    > > read-only makes files become marked read-only. Perfectly sensible,
    > > except that if you then remount the filesystem rw at resume time, all
    > > those files are still marked ro and userspace crashes and burns. Not
    > > unfixable, I'll agree, but there is more work to do there.
    > There are other solutions, though. One is that we could export a
    > system call interface which freezes a filesystem and prevents any
    > further I/O. We mostly have something like that right now (via the
    > the write_super_lockfs function in the superblock operations
    > structure), but we haven't exported it to userspace.

    It is exported on XFS ;-)

    > We would also need a similar interface to freeze any block device I/O,
    > in case you have a database running and doing direct I/O to a block
    > device. (Or again, we could simply not support that case; how many
    > people will be running running a database accessing a block deivce on
    > their laptop?)

    block device I/O uses generic_file*whateveriscurrenthere*_write, which
    checks for the freeze flag, so the infrastructure for that is there

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      Last update: 2007-04-27 12:13    [W:0.020 / U:5.204 seconds]
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